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		<h1 id="0032-menus-vii---adding-accelerator-keys-to-menuitems">0032: Menus VII - Adding Accelerator Keys to MenuItems</h1>

<div class="screenshot-frame">
	<div class="frame-header">
		Results of this example:
	</div>
	<div class="frame-screenshot">
		<figure>
			<img id="img0" src="../images/screenshots/012_menus/menu_16.png" alt="Current example output" />		<!-- img# -->
			
			<!-- Modal for screenshot -->
			<div id="modal0" class="modal">																	<!-- modal# -->
				<span class="close0">&times;</span>															<!-- close# -->
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				<div id="caption"></div>
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			var modalImg = document.getElementById("img00");													// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
			// Get the <span> element that closes the modal
			var span = document.getElementsByClassName("close0")[0];											// close#
			
			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>
			<figcaption>
			Current example output
			</figcaption>
		</figure>
	</div>

	<div class="frame-terminal">
		<figure class="right">
			<img id="img1" src="../images/screenshots/012_menus/menu_16_term.png" alt="Current example terminal output" />		<!-- img#, filename -->

			<!-- Modal for terminal shot -->
			<div id="modal1" class="modal">																				<!-- modal# -->
				<span class="close1">&times;</span>																		<!-- close# -->
				<img class="modal-content" id="img11" />																		<!-- img## -->
				<div id="caption"></div>
			</div>
			
			<script>
			// Get the modal
			var modal = document.getElementById("modal1");																	// modal#
			
			// Get the image and insert it inside the modal - use its "alt" text as a caption
			var img = document.getElementById("img1");																		// img#
			var modalImg = document.getElementById("img11");																// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
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			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>

			<figcaption>
				Current example terminal output (click for enlarged view)
			</figcaption>
		</figure>
	</div>

	<div class="frame-footer">																								<!-- ------------- filename (below) --------- -->
		The code file for this example is available <a href="https://github.com/rontarrant/gtkd_demos/blob/master/012_menus/menu_16_accel_menus.d" target="_blank">here</a>.
	</div>
</div>

<h2 id="imports">Imports</h2>

<p>First things first… We need the <code class="language-plaintext highlighter-rouge">AccelGroup</code> class and a couple of <code class="language-plaintext highlighter-rouge">enum</code>s, so we bring them in:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">import</span> <span class="n">gtk</span><span class="p">.</span><span class="n">AccelGroup</span><span class="p">;</span>
<span class="k">import</span> <span class="n">gdk</span><span class="p">.</span><span class="n">c</span><span class="p">.</span><span class="n">types</span><span class="p">;</span>
</code></pre></div></div>

<p>Make note: That’s another <strong><code class="language-plaintext highlighter-rouge">gdk</code></strong> not <code class="language-plaintext highlighter-rouge">gtk</code> library and from that we get these <code class="language-plaintext highlighter-rouge">enum</code>s:</p>

<h3 id="accelflags">AccelFlags</h3>

<ul>
  <li><code class="language-plaintext highlighter-rouge">VISIBLE</code> (shows on the <code class="language-plaintext highlighter-rouge">MenuItem</code>), and</li>
  <li><code class="language-plaintext highlighter-rouge">LOCKED</code> (can’t be remapped on the fly).</li>
</ul>

<h3 id="modifiertype">ModifierType</h3>

<ul>
  <li><code class="language-plaintext highlighter-rouge">SHIFT_MASK</code> (Shift key),</li>
  <li><code class="language-plaintext highlighter-rouge">LOCK_MASK</code> (usually the Caps Lock key),</li>
  <li><code class="language-plaintext highlighter-rouge">CONTROL_MASK</code> (Control Key), and</li>
  <li><code class="language-plaintext highlighter-rouge">MOD1_MASK</code> (usually the Alt key).</li>
</ul>

<p>We’ll get to their use in a moment, but right now let’s take a quick look at…</p>

<h2 id="the-accelgroup">The AccelGroup</h2>

<p>Because all accelerator keys are used when the <code class="language-plaintext highlighter-rouge">Window</code> has focus, the <code class="language-plaintext highlighter-rouge">AccelGroup</code> needs to be declared in, instantiated in, and added to the <code class="language-plaintext highlighter-rouge">Window</code> object:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">class</span> <span class="n">TestRigWindow</span> <span class="p">:</span> <span class="n">MainWindow</span>
<span class="p">{</span>
	<span class="nb">string</span> <span class="n">title</span> <span class="p">=</span> <span class="s">"Multiple Menus Example"</span><span class="p">;</span>
	<span class="n">AccelGroup</span> <span class="n">accelGroup</span><span class="p">;</span>

	<span class="k">this</span><span class="p">()</span>
	<span class="p">{</span>
		<span class="k">super</span><span class="p">(</span><span class="n">title</span><span class="p">);</span>
		<span class="n">setDefaultSize</span><span class="p">(</span><span class="mi">640</span><span class="p">,</span> <span class="mi">480</span><span class="p">);</span>
		<span class="n">addOnDestroy</span><span class="p">(&amp;</span><span class="n">quitApp</span><span class="p">);</span>

		<span class="n">accelGroup</span> <span class="p">=</span> <span class="k">new</span> <span class="n">AccelGroup</span><span class="p">();</span>
		<span class="n">addAccelGroup</span><span class="p">(</span><span class="n">accelGroup</span><span class="p">);</span>

		<span class="n">AppBox</span> <span class="n">appBox</span> <span class="p">=</span> <span class="k">new</span> <span class="n">AppBox</span><span class="p">(</span><span class="n">accelGroup</span><span class="p">);</span>
		<span class="n">add</span><span class="p">(</span><span class="n">appBox</span><span class="p">);</span>
		
		<span class="n">showAll</span><span class="p">();</span>
		
	<span class="p">}</span> <span class="c1">// this()</span>
	
	
	<span class="kt">void</span> <span class="n">quitApp</span><span class="p">(</span><span class="n">Widget</span> <span class="n">w</span><span class="p">)</span>
	<span class="p">{</span>
		<span class="c1">// do other exit stuff here if necessary</span>
		
		<span class="n">Main</span><span class="p">.</span><span class="n">quit</span><span class="p">();</span>
		
	<span class="p">}</span> <span class="c1">// quitApp()</span>
	
<span class="p">}</span> <span class="c1">// TestRigWindow</span>
</code></pre></div></div>

<p>Notice also that it gets passed to the <code class="language-plaintext highlighter-rouge">AppBox</code> constructor which passes it along to the <code class="language-plaintext highlighter-rouge">MyMenuBar</code> constructor, then <code class="language-plaintext highlighter-rouge">FileMenuHeader</code>, <code class="language-plaintext highlighter-rouge">FileMenu</code>, <code class="language-plaintext highlighter-rouge">EditMenu</code>, etc. down the line until it’s available to each individual <code class="language-plaintext highlighter-rouge">MenuItem</code> constructor like this:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">class</span> <span class="n">ExitItem</span> <span class="p">:</span> <span class="n">MenuItem</span>
<span class="p">{</span>
	<span class="nb">string</span> <span class="n">itemLabel</span> <span class="p">=</span> <span class="s">"Exit"</span><span class="p">;</span>
	<span class="kt">char</span> <span class="n">accelKey</span> <span class="p">=</span> <span class="sc">'q'</span><span class="p">;</span>
   
	<span class="k">this</span><span class="p">(</span><span class="n">AccelGroup</span> <span class="n">accelGroup</span><span class="p">)</span>
	<span class="p">{</span>
		<span class="k">super</span><span class="p">(&amp;</span><span class="n">doSomething</span><span class="p">,</span> <span class="n">itemLabel</span><span class="p">,</span> <span class="s">"activate"</span><span class="p">,</span> <span class="kc">true</span><span class="p">,</span> <span class="n">accelGroup</span><span class="p">,</span> <span class="n">accelKey</span><span class="p">,</span> <span class="n">ModifierType</span><span class="p">.</span><span class="n">CONTROL_MASK</span><span class="p">,</span> <span class="n">AccelFlags</span><span class="p">.</span><span class="n">VISIBLE</span><span class="p">);</span>
		<span class="c1">//addOnActivate(&amp;doSomething);</span>
		
	<span class="p">}</span> <span class="c1">// this()</span>
	
	
	<span class="kt">void</span> <span class="n">doSomething</span><span class="p">(</span><span class="n">MenuItem</span> <span class="n">mi</span><span class="p">)</span>
	<span class="p">{</span>
		<span class="n">writeln</span><span class="p">(</span><span class="s">"Quitting... Bye."</span><span class="p">);</span>
		
		<span class="n">Main</span><span class="p">.</span><span class="n">quit</span><span class="p">();</span>
		
	<span class="p">}</span> <span class="c1">// exit()</span>
	
<span class="p">}</span> <span class="c1">// class ExitItem</span>
</code></pre></div></div>

<p>A less cumbersome way to do this would be with a singleton, but we’ll have that discussion next week.</p>

<p><em>Another thing to note: Instead of connecting the callback here, we pass it to the super-class. I left the <code class="language-plaintext highlighter-rouge">addOnActivate()</code> line there—just commented out—as a reminder. Naturally, you can un-comment it to see what happens.</em></p>

<h2 id="what-are-all-those-arguments">What are all those Arguments?</h2>

<p>The major departure from earlier examples is, as mentioned, the call to the super-class. One by one, they are…</p>

<h3 id="delegate">Delegate</h3>

<p>This is exactly the same argument we would pass to a signal hook-up function, which is the name of the callback function, preceded by an ampersand (&amp;).</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="k">delegate</span><span class="p">(</span><span class="n">MenuItem</span><span class="p">)</span> <span class="n">dlg</span>
</code></pre></div></div>

<p>In this case, it’s: <code class="language-plaintext highlighter-rouge">&amp;doSomething</code>.</p>

<h3 id="label">Label</h3>

<p>This is the text that’ll appear on the <code class="language-plaintext highlighter-rouge">MenuItem</code>:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">string</span> <span class="n">label</span>
</code></pre></div></div>

<p>And for us (have a look at the initialization section of this class) it ends up being <code class="language-plaintext highlighter-rouge">"Exit"</code>.</p>

<h3 id="action">Action</h3>

<p>This next argument takes the place of assigning a signal when dealing with a <code class="language-plaintext highlighter-rouge">MenuItem</code>:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">string</span> <span class="n">action</span>
</code></pre></div></div>

<p>I can think of no reason to use any signal other than <code class="language-plaintext highlighter-rouge">“activate”</code>… although you might. (And if you do, please post about it either on <a href="https://forum.dlang.org/">the D Language forum</a> or <a href="https://forum.gtkd.org/groups/GtkD/">the GtkD forum</a> so we can all add a new technique to our toolbox.)</p>

<h3 id="mnemonic">Mnemonic</h3>

<p>No need to get deep here, just set this to <code class="language-plaintext highlighter-rouge">true</code>:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">bool</span> <span class="n">mnemonic</span>
</code></pre></div></div>

<h3 id="accelgroup">AccelGroup</h3>

<p>This is what we passed down from the <code class="language-plaintext highlighter-rouge">RigTestWindow</code>, the object that connects all the keyboard shortcuts to the application’s <code class="language-plaintext highlighter-rouge">Window</code>:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">AccelGroup</span> <span class="n">accelGroup</span>
</code></pre></div></div>

<h3 id="the-keyboard-shortcut-itself">The Keyboard Shortcut Itself</h3>

<p>This is the letter key used in combination with <code class="language-plaintext highlighter-rouge">ModifierType</code> (the next argument) to designate the entire keyboard shortcut:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">char</span> <span class="n">accelKey</span>
</code></pre></div></div>

<p>And for our example here, it’s <code class="language-plaintext highlighter-rouge">'q'</code> for <em>Exit</em>… Well, the standard is <em>Quit</em>, but whatever.</p>

<h3 id="modifiertype-1">ModifierType</h3>

<p>This decides which qualifier key is held while pressing the letter key:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">ModifierType</span><span class="p">.&lt;</span><span class="n">MODIFIER</span><span class="p">&gt;</span>
</code></pre></div></div>

<p>These take the form of <code class="language-plaintext highlighter-rouge">ModifierType.CONTROL_MASK</code> or <code class="language-plaintext highlighter-rouge">ModifierType.SHIFT_MASK</code> and can be <strong>OR</strong>’ed together like this: <code class="language-plaintext highlighter-rouge">ModifierType.CONTROL_MASK | ModifierType.SHIFT_MASK | ModifierType.MOD1_MASK</code> if you want someone to hold down <strong>Ctrl-Alt-Shift-KEY</strong>. We looked at the possible values for <code class="language-plaintext highlighter-rouge">ModifierType</code> right at the beginning of this post (in case you need to refer back).</p>

<h3 id="accelflags-1">AccelFlags</h3>

<p>And lastly, the <code class="language-plaintext highlighter-rouge">AccelFlags</code> argument:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">AccelFlags</span><span class="p">.</span><span class="n">VISIBLE</span>
</code></pre></div></div>

<p>This flag is optional and you can actually leave it out. It’s main use seems to be <code class="language-plaintext highlighter-rouge">AccelFlags.LOCKED</code> which is used when you don’t want users messing with your shortcut keys.</p>

<h2 id="conclusion">Conclusion</h2>

<p>So, yeah, it takes a bit of extra coding to make these work:</p>

<ul>
  <li>from stuffing an <code class="language-plaintext highlighter-rouge">AccelGroup</code> into your main <code class="language-plaintext highlighter-rouge">Window</code>,</li>
  <li>passing it all the way down to the <code class="language-plaintext highlighter-rouge">MenuItem</code> objects so they have access when they instantiate, and</li>
  <li>coming up with that long list of arguments to pass to the super-class constructor.</li>
</ul>

<p>But your users will thank you. And speaking of thanks…</p>

<p>Thanks for reading and do please come back for the next post. Until then…</p>

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